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Some
viewers, get to this page because they are caring for an orphaned wild
raccoon. But the advice is
just as good of you have a nuisance raccoon problem, keep one as a family
pet, or if you just want to understand the risk that Baylisascaris-exposure
might cause to you and your children and the things you can do to minimize
that risk.

If you would like to personally advance public health and veterinary knowledge about this problem, go here

If you are interested to learn what vaccinations captive raccoons might require, go here

Intestinal
roundworms are nematode parasites. Most every species of animal (host)
– including humans - have their own special types of nematodes
that have adapted to thrive in their intestinal environment and that
have developed successful ways of transferring from one host to another.

Raccoons
are no different. Their intestinal roundworm is Baylisascarisprocyonis. Over the eons that they have existed together,
the raccoons and this parasite have worked out their relationship well
enough that the raccoons normally suffer no health issues when the parasite
is present in their intestines in reasonable numbers. The threat to
people occurs because of the special way this parasite has adapted to
move from one raccoon to another and the cleverness of raccoons in adapting
to our urban landscape (high
ecological plasticity) Raccoons are exceptionally clever,
adaptable omnivores, equipped with thumbs which allow them to, among
other things, open garbage containers and food receptacles.

Although
raccoons are native to North America, you might not know that they are
now common in central Europe and Japan and parts of the former USSR.
Unfortunately, they have brought the baylisascaris parasites along with
them. You can read about that here.

Who
Is Most At Risk ?What
Are The Actual Chances Of Me Or My Family Becoming Infected With This
Parasite ?

Anyone who inhabits an area where raccoons live is potentially at risk.
Young children and mentally people are at higher risk of infection because
they are more likely to put contaminated fingers, soil, water or objects
into their mouth. That is the only way we know of to become infected.
You can read accounts of two typical human cases here.

This
same feces-to-oral contamination rout is how dog roundworms (Toxocara) pass to
humans. Anywhere between 1-10% of children show evidence in their blood
of having ingested dog toxocara eggs. The more likely children are to
play in dirt, the more likely the exposure. (ref)

Scientists
know much less about the frequency of humans exposure to Baylisascaris.
In a 2003 study of children in the Chicago area, 30 of 389 (8%)
showed evidence of exposure to Baylisascaris in their blood. (ref)

There were problems with the blood tests used in this study. The authors have told me that exposure of these children to dog roundworm eggs may have been inadvertently attributed to exposure to raccoon roundworm eggs. The CDC
has stated that “predictive value of available serological tests
[available at that time] are unknown.” (ref)

Fewer
than 20 serious human brain infections (encephalitis)
from raccoon roundworm have been documented in the last 30 years. Over
the same period, there have been an average of 55 lightning fatalities
in the US each year and 75 cases of amoebic encephalitis due to swimming
in dirty water.

Of
course, if you or your family handle or expose yourself to raccoon waste
in unsanitary ways – all bets are off.

Is
The Risk Of Infection Getting Greater ?

Yes.
That is because the urban raccoon population is quickly increasing.

Public
health departments harp on the dangers of baylisascaris in an attempt
to deal with rising populations of marauding urban raccoons and they
are correct in doing so. But the dangers of these large populations
of clever, unsupervised animals is really much broader that that one
threat. Abnormally high raccoon populations disrupt Nature’s harmony
and balance. Much like feral cat colonies they destroy the smaller wildlife
and bird population and bring the threat of raccoon-borne
rabies as well as raccoon-borne
Lyme disease and raccoon-transmitted
leptospirosis into your neighborhood environment.

Feral (stray) cat colonies and urban raccoon
problems go hand-in-hand. It is not only the cats that come at night to feed at the feeders
that well-meaning people supply for those cats. (photo)

There
is a second, potentially greater, risk. Baylisascaris can also live
in the intestines of dogs. As dogs and urban raccoons mingle, there
is a real possibility the more dogs will become infected. You
can read about that threat here and here.

Dogs relieve themselves wherever convenient – not in specific
latrines. In doing so, dogs contaminate the environment much more widely
and make human exposure to their parasite eggs considerably more likely.

What
Is The Natural Life Cycle Of This Parasite ?

Baylisascaris
is a species of roundworm or ascarid. It lives its whole adult life
in the small intestine of raccoons. All ascarid parasites do little
damage in their adult form. They absorb the nutrients they need from
the partially digested food in the raccoons intestine - not by damaging
the raccoons’ intestine itself. So unless the raccoon has an usually
large number of these parasites, they cause it little or no harm.

Baylisascaris
exists as either a male or a female worm. When female worms mature (in
about a month or two), they begin to lay an enormous number
of eggs that leave the raccoon mixed with its stool. Raccoons under
a year of age are usually the largest shedders of these eggs. When raccoon
stool is fresh, the eggs are not infective. But after the stool has
sat for 11-14 days, the Baylisascaris eggs have developed sufficiently
to hatch if eaten. In this infective state, in the proper conditions,
these eggs can remain infective for years.

Two
things can happen to these infective eggs. If they are accidentally
consumed by another raccoon – particularly an immature raccoon –
they can develop into new mature parasites in that animal's intestine.

A
second, probably more common thing can also occur. The infective eggs
can be consumed by another species of animal – usually a small
rodent or perhaps a bird. In those non-raccoon species, the eggs do
hatch. But instead of staying in the new host’s intestines, the
larval parasites migrate throughout the host’s body. They are
eventually walled off in small islands (cysts)
of inflamed tissue (eosinophilic
granulomas). Perhaps more frequently than with other
ascarids that share this type of life cycle, Baylisascaris granulomas
occur in nerve tissue or the brain. These debilitated rodents and birds
are easy prey for raccoons. When they are eaten, the encysted parasites
in these small prey animals find their way back to the raccoon’s
intestines where the cycle begins anew.

You
can read about the parasite’s life cycle in considerably more
detail here.
(Dr. Kazcos is the premier expert on Baylisascaris)
Occasionally, the parasite will enter the eye of these non-raccoon species
causing severe damage. (ref)

Baby
raccoons as young as three months old can already be passing Baylisascaris
eggs in their stool. (ref)

Is
Baylisascaris More Common In Raccoons In Some Localities Than Others
?

Probably
so. Studies of raccoons in various parts of the US have found different
rates of infection. Baylisascaris eggs do not survive well in the dry,
hot conditions found in some areas.

Urban
raccoons are more likely to consume garbage, and dog and cat chows than
their normal infected prey animals so perhaps, they have slightly less
exposure to Baylisascaris through the prey they would normally eat.
Yet diseases of all kinds tend to spread more quickly in crowded condition.
We do not know how those two factors might interplay to influence parasite
numbers.

Because immature and young-of-the-year raccoons tend to have more parasites,
Baylisascaris seem to be more common in late summer and fall when that
year’s raccoon offspring are maturing and prevalent.
You can read two articles that discuss some of these points here and
here.

What
Happens When These Parasites Get Into A Human Being ?

Should
you, or a family member inadvertently swallow an infective Baylisascaris
egg, it will continue with its development just like it would have in the
rodent or bird intermediate host that it was designed to infect.

It
will hatch in your digestive system, the larva will penetrate through
the intestinal wall and begin its wandering throughout the body. All
intermediate hosts recognize this larva as a foreign invader (foreign
protein) and attempt to wall it off with defensive cells
and tissue (granuloma). If this granuloma forms in a non-critical area,
it is not of much importance. With extended time, your body defenses
will kill and absorb it. If, however, this granuloma forms in the brain,
eyes, or spinal cord (ref) it will cause severe damage. Often, that damage, once apparent, is permanent;
occasionally it is not. (ref)

It
is quite likely that (as is the case with most other
ascarids(ref
1 & ref
2), this occurs with no apparent symptoms in the victim and
with no one the wiser that such a thing occurred. If, however, the Baylisascaris
larva lodges in the victim’s brain or eye, the body’s attempt
to destroy it can damage that organ quite a bit. In those cases, loss
of vision, paralysis and mental changes all occur. Even dog roundworms
occasionally cause this. (ref)

One of the body’s defense cells, responsible for fighting foreign
invaders like Baylisascaris, is the eosinophil. A high eosinophil blood
count (eosinophilia) is often the most
reliable clue to physicians that a parasite like Baylisascaris might
be responsible.

Should
large numbers of these raccoon roundworm eggs be eaten, the symptoms
are likely to be much like those seen in children (or
adults) who have consumed large numbers of dog roundworm
eggs (Toxocara
canis) by accident. (visceral
larval migrans).You can read about that problem here.

I
has been difficult for physicians to diagnose Baylisascaris infections
in humans with accuracy. However, a recent blood test (RA
ELISA) may be effective in doing so. You can read about
that test here.

What
Adds To A Person's Risk ?,

The
first, and most important risk fact is the number of raccoons living
in your immediate area. In some suburbs and cities in the US, raccoon
populations are enormously dense – up to 383 raccoons/square mile (238/km2).
The problems is particularly severe in California and Florida. (ref
1 & ref 2)

Young
children are most at risk of consuming parasite eggs of all
kinds – including Baylisascaris. This is because of their tendency
to put things in their mouth, their curiosity, and their inability to
stand. Young of all species also lack developed ways of fighting these
parasite larva once they enter the body. (ref)

People
who practice poor hygiene for one reason or another are at greater risk. These can be folks
with diminished mental capacities or those whose work demands that they enter
contaminated areas frequently, or who increase their exposure to raccoon
feces for one reason or another. Similar occupational hazards exist
when it comes to dog roundworms. You can read more about that issue here.

What
Specific Steps Can I Take To Prevent Exposing Myself Or My Loved Ones
To This Parasite ?How Can I Get Raccoons To Leave And Live Somewhere Else ?

Spread
information about the dangers of feeding raccoons to people you know.

This
is basically a people problem, not a raccoon problem. Raccoons are one
of the cutest of wild animals. One look at a baby raccoon or momma raccoon
and her brood begging for food at your door is enough to melt the coldest
of hearts. It is just natural that we would want to feed and shelter
them. It is not apparent to most people that doing so upsets the natural
balance of Nature and exposes our families to disease. There is little
that one person or one family can do on their own to decrease raccoon
numbers. It takes the combined work of an entire community.

Dry
dog and cat chow, left outside for your pets, is the biggest single
factor allowing urban raccoon populations to explode. Dogs and cats
do perfectly well on one or two feedings a day. There is no need to
maintain outside feeders. Feeding stray cats and dogs, or having neighbors
that do, just perpetuates the pet over-population problem. Maintaining
feral cat populations is very short sighted. It has just as negative
an effect on long-term pet and human health and well being as feeding
raccoons. Read more about that here.

If
you do feed your pets outside, taking the food in after 4PM is helpful.
However, in many localities, raccoons are becoming daytime feeders as
well as night time feeders. The old idea that raccoons, out in the daytime, have either distemper or rabies is no longer true.

Secure
Your Trash Receptacles.

Raccoons
are amazingly clever and persistent in getting to garbage and human
food sources. They have grasping abilities that no other American wildlife
possesses. They are extremely clever and patient when they know that
a food source is near by. Long ago, urban raccoons learned to associate
the mere presence of humans will easy food. Clean up after your family
picnics. Don’t rely on park trash receptacles – take the
waste home with you instead. See to it that dumpster lids remain closed.
Put your trash can in a wooden or metal frame that prevents it from
being tipped over when raccoons come a calling.

Keep
your property as free of nesting and hiding sites as you can.

Cover
any entrances to crevices, nooks and crannies with chicken wire. Do
the same for any entrances into your roof or attic. (When
blocking a potential entrance, bend the chicken wire into a 90 degree
angle that extends 12 inches on the ground ahead of the opening. Raccoons
will easily dig under a barrier placed at ground level; but they will
not begin digging 12 inches in front of the entrance.)

Firewood piles are an ideal place for raccoons to live in and for them
to establish latrines on. Consider keeping the firewood in a shed, or
on an off-the-ground rack surrounded with chicken wire. Remove as much
trash, brush and items that raccoons might hide in from your property
as possible.

But
remember, no matter how inviting raccoons might find your property to
live on, they will not live there unless they have nearby access to
food.

Use
flashing on objects raccoons might climb.

Raccoons
gain access to attics and roof crevices by climbing trees. Cut and trim
back branches that come anywhere close to the roof of your house. A
16-inch surround of roof flashing secured by a nail will prevent raccoons
from scaling these trees. (here
is a photo)

Take
in or empty bird feeders at sundown.

Chemical
Repellents are ineffective.

I
have not found any chemical animal repellents to will dissuade raccoons
from using a food source when they are hungry. The same goes for ultrasonic
contraptions and motion-activated devices – Raccoons soon get
over their initial fear of these new gadgets and completely ignore them.

What
About Trapping And Relocation ?

Raccoons
are rather easy to catch in live traps. Traps work well to eliminate
a particular nuisance individual or small band of raccoons. However,
there are really no suitable places to relocate these animals to and
if your home and yard remain attractive to raccoons, new ones will soon
appear.

Keep
your dog on a monthly heartworm preventative that also controls Toxocara
canis.

Dogs
can serve as either the final or the intermediate host of Baylisascaris.
That means that the raccoon parasite can both make your pet ill and
live in its intestine as a source of infection to other family members.
That should not be a problem if you keep your pets on a heartworm preventative
all year long. Cats do not appear to be suitable hosts for the adult
worm – but they are equally susceptible to disease caused by the
immature Baylisascaris larva.

How
Long Do These Parasite Eggs Last In The Environment - How Tough Are
They ?

In
relatively moist, shaded conditions, Baylisascaris eggs will last
a very long time (years) - longer
than you would wish to wait.

Remember,
Baylisascaris eggs in fresh raccoon feces are not the threat. They
must develop, on the ground or in the soil, over a 2-4 week period
before they can infect another animal (or person).

Near-boiling
water temperature will kill baylisascaris eggs. (ref)
but drying , winter temperatures
or bleach disinfection have little effect on them. (ref) They are likely to even survive a trip through your drain pipes and on to your local sewage plant. (ref)

Other animal
roundworm eggs are more susceptible to ammonia than to bleach; we do not know but perhaps
Baylisascaris would be as well. (ref)

How
Can I Effectively Clean Up An Area Of Raccoon Feces And Destroy
The Parasite’s Eggs ?

The
best method to deal with a contaminated area or raccoon latrine
is to use a square-ended coal shovel to scrape up the feces and
about the top 1-2 inch of soil. First lightly mist the area with
a garden hose or spray bottle of ammonia solution to keep dust down.

Place
what you remove into a heavy-duty garden leaf bag and put that in your trash
can. When cleaning an area, wear a face mask (N95-rated)
and gloves. Keep children, pets and bystanders away. When you are done, put all the clothes you wore through a hot water washer and dryer cycle. Then take a shower, wash your hair, clean your fingernails. Do the job on a day that is
not windy.

Raccoons often defecate in elevated areas, decks, attics or the
bases of trees that are hard to clean. You will need to wear nitrile
gloves when handling these contaminated objects. Never use a leaf
blower or anything that would scatter the eggs even more.

An
alternative is to cover the area with an additional 4-6 inches of
new soil, lay down plastic sheeting or some other impervious material.

Items
that can be rinsed with soapy water should be thoroughly scrubbed
and the rinse water poured down the toilet. Throw away all items
used in the process.

Hard smooth surfaces can be disinfected with
boiling water or a steam jenny (Some of these
jennys reach 325F at the nozzle – so be careful and test a small piece of
carpet or sofa material to be sure you do not ruin them if you are steaming in or near the home or attic).

A propane torch works equally well where there is no fire hazard. I one had a neighbor burn down his garage while attempting to flame a wasp nest - be careful !

If
you do not want to face these potential hazards, hire an experienced,
bonded cleaning company to do it for you.

Are
There Medications That Will Effectively Rid Raccoons Of Baylisascaris
?

If
you keep raccoons, raise orphan ones or if you insist on feeding wild ones,
mature Baylisascaris are rather easy to kill. Just assume that all raccoons have them.

I
suppose that a Baylisascaris-free raccoon over-population is better
than a Baylisascaris-carrying raccoon population and if you rehabilitate wildlife you
need to be certain that your wards are free of this parasite.
If you choose that approach, you can read about the medications that
are effective in killing Baylisascaris in raccoons here.

Monthly heartworm prevention tablets, designed for dogs would probably
also be effective. You can read a study on one brand here.
Ivermectin products are equally effective. (ref)

If you keep raccoons, there
may be some danger in assuming that a raccoon that is not shedding
Baylisascaris eggs in its stool is truly free of the parasite once
it has been wormed. It might be that the medication has simply blocked
the parasites ability to produce eggs at that time. The most accurate
determination that a raccoon is free of Baylisascaris is to run
a PCR test on its stool. (ref)
this test is available commercially. (ref)

Are There Effective Treatments After This Parasite Enters The
Brain Of Animals Or Humans ?

Once
Baylisascaris has entered the brain, eyes or some other point in
the nervous system of a non-raccoon species, treatment is very difficult.
That is because most of the damage that is occurring is not due
to the parasite itself, but to the body’s reaction to the parasite’s
presence. Even when that parasite is destroyed by medications, the
offending presence of the dead parasite is still there. In fact,
if the parasite disintegrates, the situation can be made worse

So
treatments focus on blocking the body’s immune response with
medications like prednisone
and providing supportive nursing care. In certain instances, such
as a Baylisascaris larva present in the eye, it might be removed
surgically or destroyed with a laser. When attempts are made to
kill the larva with medications, it is often albendazole that is
used. (ref1&
ref
2)